FIG. 5 shows a structure of a prior art semiconductor laser array. The reference numeral 1 designates a p type GaAs semiconductor substrate. The numeral 8 designates an n type electrode. The numeral 9 designates a p type electrode. The numeral 13 designates a current blocking layer comprising n type GaAs, the numeral 14 designates a cladding layer comprising p type Al.sub.0.45 Ga.sub.0.55 As, the numeral 15 designates an active layer comprising p type Al.sub.0.15 Ga.sub.0.85 As, the numeral 16 designates a cladding layer comprising n type Al.sub.0.45 Ga.sub.0.55 As, and the numeral 18 designates a laser light spot obtained in the laser oscillation state.
In a semiconductor laser array of such a structure, the p type semiconductor substrate 1, the n type current blocking layer 13, and the p type cladding layer 14 are constituted to produce a p-n-p conductivity type structure, and thus the current is blocked. The current only flows concentratedly through the stripe groove portion of the current blocking layer 13, and as a result a laser oscillation occurs at the region of the active layer 15 above the stripe groove. In other words, a semiconductor laser array of two point light emission can be produced by producing two stripe grooves in an element.
Generally, the laser light of a semiconductor laser is polarized in a TE wave having an electric field vector in a direction parallel to the active layer 15 in a plane vertical to the advancing direction of the laser beam, and there exists almost no TM wave component having an electric field vector in the direction vertical thereto. Accordingly, when a two point light emission array structure is constituted in a semiconductor laser having an active layer 15 whose surface is flat and is parallel with the substrate 1, the TE waves of the respective laser lights are perfectly directed in the same direction. Furthermore, in this structure the active layer 15 continues linearly between the two stripe grooves, this active layer portion functioning as a waveguide of the laser light.
When the two stripe grooves are provided adjacent to each other within about 10 micron, the two laser lights coincide with each other in the TE wave direction, and thus both laser lights are optically combined with each other. Accordingly, there occurs a so-called phase synchronous oscillation in which oscillations are conducted at the same wavelengths with a constant phase relation.
In such a prior art semiconductor laser array, if the distance between the two laser light spots is reduced to below 10 micron, it is difficult to utilize the two laser lights independently.